Is Aether Herder legal in Standard, Modern, and Commander?

Aether Herder is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Pauper.

What type of card is Aether Herder?

Aether Herder is a Creature — Elf Artificer Druid. Its oracle text reads: "When this creature enters, you get {E}{E} (two energy counters). Whenever this creature attacks, you may pay {E}{E}. If you do, create a 1/1 colorless Servo artifact creature token."